Some software systems define a security boundary for users in the system, referred to herein as a forest. The forest may include one or more directory servers, one or more mailbox servers, and one or more client computing devices running personal information manager (PIM) applications. The mailbox server(s) may maintain mailboxes for user accounts, which may have associated PIM data that can be shared with other users having accounts in the forest. However, forests typically have one or more security features that prevent users from one forest from sharing/accessing PIM data with users of another forest. Although some conventional systems are discussed, this background is not intended to identify problems that must be addressed by the claimed subject matter.